Researchers looked at the schedules of more than 500 CEOs around the world by having executive assistants track all activities that lasted more than 15 minutes, and found that CEOs spend 85 percent of their time with other people.

As for whether this is a good use of time, it all depends upon who the CEO is spending time with. According to the Wall Street Journal:

"[In a] sample of 94 Italian CEOs, the researchers found that the way an executive budgets his or her time strongly correlated with a firm's profitability and productivity, measured as revenue per employee. The key to a company's performance was with whom CEOs met. Meeting with external figures didn't help a firm's productivity, they found. Better performance came from more internal meetings."

This means finding the "optimal inside/outside" balance. When CEOs gain more power and visibility, usually they'll spend more time outside the firm, which doesn't help the company's performance, according to the paper:

"Time devoted to activities that mostly benefit the firm is more strongly correlated with productivity than time devoted to activities that mostly yield private benefits."